As recognized in co-pending application Ser. No. 192,032 filed Sept. 29, 1980 now U.S. Pat. No. 4,354,777 (the disclosure of which is hereby incorporated by reference herein) conventional high-pressure transfer devices will have unacceptable leakage, and in fact may become non-operational, as a result of radial deflection of the transfer device housing under high-pressure conditions. In said co-pending application this tendency of the housing to radially deflect was counteracted by applying a radially inward force to the high-pressure portions of the housing. While such an arrangement is successful in performing this intended function, leakage may still be more than desired.
According to the present invention, a high-pressure transfer device (and methods of utilization thereof) is provided which can reduce leak volume even when the device is operated at extremely high-pressure differentials (e.g. 50 to 100 bars), and will not bind as a result of housing radial deflection. According to the present invention the high-pressure transfer device is constructed so that deflection of the housing is permitted, yet the construction is such that such deflection does not affect the amount of leakage, nor will the deflection result in binding of the rotor.
While the device according to the present invention is particularly adaptable for use where high-pressure differentials are encountered, it has broader applicability. In conventional high-pressure transfer device, even when operated under relatively small pressure differentials, only a small amount of wear of the rotor or other operative components can be tolerated. Conventionally only 1/10 inch of wear off the rotor can be compensated for without undue leakage. According to the present invention, however, much larger amounts of wear can be compensated for. For instance, wear on the order of 1/2 to 3/4 inch of various component parts can be tolerated without unacceptable leakage, making the device according to the present invention advantageous for all situations where solids material in a suspension is to be transported, although the device is particularly advantageous for conveying coal, oil shale, mineral ores, etc. from the face to the surface of underground mines, and for pumping hard particulate material (such as manganese nodules) from an ocean floor (e.g. 15,000 feet below sea level) to the surface.
The high-pressure device according to the present invention includes a pocketed rotor having a plurality of diametrically through-going pockets, and rotatable about an axis. A housing encloses the rotor, the housing having an exterior periphery and four ports disposed around the exterior periphery for registry with inlets to and outlets from the pockets. Means are provided for mounting the rotor in the housing for rotation with respect to the ports about the axis of rotation, and screen means are provided for screening particulate material above a predetermined size out of the liquid passing through at least one of the ports. A large clearance volume is provided between the rotor and the housing, and sealing means are disposed in the large clearance volume. The sealing means provide minimized leakage of liquid between the rotor and housing while allowing relative rotational movement between the rotor and housing, and the sealing is unaffected by radial deflection of the housing.
The sealing means associated with the high-pressure device comprise at least one high-pressure shoe associated with the high-pressure inlet and at least one high-pressure shoe associated with the high-pressure outlet, and at least one low-pressure shoe associated with the low-pressure inlet and at least one low-pressure shoe associated with the low-pressure outlet. Each of the shoes is disposed between the rotor and housing and has at least one opening communicating with its respective port. The shoes may be continuous, running the entire axial extent of the transfer device with an opening provided therein for each rotor pocket, or may be segmented, each shoe being associated with only one rotor pocket. Normally the high-pressure sealing means will be segmented so that one shoe is associated with each rotor port, while the low-pressure shoes will each extend the entire axial length of the transfer device. Preferably the high-pressure shoes are made of a less wear-resistant material than the rotor, and are mounted (along with the low-pressure shoes) for axial movement so that they may be removed and replaced when worn.
The rotor is cylindrical and has at least five diametrically through-going pockets. Each pocket has an inlet and an outlet and the inlets and the outlets of the pockets are positioned so the pockets are spaced angularly around the exterior periphery of the rotor in such a way that an inlet or an outlet of one pocket is in direct liquid communication with each of the ports at all times. The screen means preferably comprises an interior screen disposed within each of the pockets, which interior screen can take any suitable form for performing its intended function. The pockets may extend straight through, or may be deflected axially and interweaved with each other, or may be otherwise constructed in any functional manner.
The transfer device further comprises means for applying a force proportional to the liquid pressure at a particular point for maintaining the sealing means in sealing relationship with the rotor. Such pressure-responsive force application means comprise a plurality of pressure compensators, each compensator having a pressure-responsive element operatively disposed between the housing and the sealing means and in liquid communication with the volume between the sealing means and rotor. A pressure compensator is associated with each shoe at each area of communication of each port with each pocket, and at least two accessory pressure compensators are associated with each high-pressure shoe, one on either side of the high-pressure inlet or outlet.
Preferably purge means are provided for introducing a purging liquid between each of the high-pressure shoes and the rotor, such as through the accessory pressure compensators. In such a case, the accessory pressure compensators communicate with the volume between the rotor and the shoes through an orifice, with high-pressure liquid being supplied thereto through a separate orifice for each, the construction of each of the orifices depending upon the particular pressure at the accessory pressure compensator with which they are associated. Each rotor pocket has an inlet and outlet of given arcuate circumferential dimension .alpha., and each low pressure shoe has an arcuate segmental portion on either side of the opening therein, each arcuate segmental portion having a circumferential dimension slightly greater than .alpha.. The purge means are provided to reduce wear of the rotor and sealing means, and to prevent contamination of the pressure compensator with particulate material, and also can serve to reduce the amount of torque needed to be applied to the rotor to affect start-up.
It the primary object of the present invention to provide a high-pressure transfer device which will not leak excessively even after extended wear of the relatively rotatable components thereof, and even under high-pressure conditions causing radial deflection of the housing. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.